Study on a free electron laser in a THz region using a modulation beam emitted from a micro-field emitter

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1.We observed Smith-Purcell radiation try passing a dc-electron beam emitted from a micro field emitter on an Al grating. The beam current, and acceleration voltage were 200nA and 25-30kV, respectively The pitch of the grating was 416nm. The observed radiations were 4th harmonic one in the ultraviolet region around 350nm, 3rd harmonic one around 400nm, 2nd harmonic one around 600nm, and fundamental one around 1300nm. The wavelength of the observed Smith-Purcell radiation agrees with the smith-Purcell theory.2.To realize a free electron laser, a high frequency electron pulsed beam is necessary. We have developed a fabrication process of a p-type GaAs emitter using a wet etching for the generation of the high frequency pulsed beam. We performed the (NH4)2Sx surface treatment on GaAs a emitter. As the result, we observed a clear saturation of the emission current for the p-type GaAs emitter, because the treatment eliminated the surface oxide, improved the surface roughness, and prevent the oxidation of the surface.3.We also develop a fabrication process of a GaAs photocathode for the generation of the high frequency puked beam. We employed a Yo-Yo method for making a negative electron affinity of the GaAs surface. As the result, we have succeeded in fabricating a GaAs photocathode with a quantum efficiency of 2%.